(a) Technical Field
The present invention relates to an Fe-modified nickel-based perovskite-type catalyst including a lanthanide and an alkaline earth metal and a method for preparing same. The present invention also relates to a method for preparing a synthesis gas by a combined reforming reaction using natural gas, carbon dioxide and water in the presence of the catalyst.
(b) Background Art
With continuing high oil price, limited resources and concerns on environmental pollution, the gas to liquids (GTL) process of producing clean synthetic fuels from natural gas has attracted attentions for decades. It is expected that the synthetic oil produced from the GTL process will be an ecofriendly and economical alternative to the fossil fuel for decades to come. Also, the GTL-floating production, storage and offloading (FPSO) technique of producing synthetic oil from an offshore stranded gas field is attracting attentions (Korean Patent Publication No. 10-2011-0059306).
In the production of synthetic oil from the Fischer-Tropsch reaction, a synthesis gas including hydrogen and carbon monoxide is supplied as a reactant. An ideal H2/CO ratio of the synthesis gas for the Fischer-Tropsch reaction is 2. The synthesis gas is produced by steam reforming, carbon dioxide reforming, partial oxidation reforming using oxygen, autothermal reforming combining steam reforming and partial oxidation reforming, tri-reforming using carbon dioxide, oxygen and steam, and so forth. Reaction schemes for the respective reforming reactions are as follows.
Carbon dioxide reforming reaction (CDR)CH4+CO2→2CO+2H2 ΔH=247 kJ/mol
Steam reforming reaction (SR)CH4+H2O→CO+3H2 ΔH=208 kJ/molCH4+2H2O→CO2+4H2 ΔH=163 kJ/mol
Combined steam carbon dioxide reforming reaction (SCR)=SR+CDR
Partial oxidation reaction (POX)CH4+½O2→CO+2H2 ΔH=−38 kJ/molCH4+2O2→CO2+2H2O ΔH=−801 kJ/mol
Autothermal reforming reaction (ATR)=SR+PDX
Tri-reforming reaction=SR+PDX+CDR
The carbon dioxide reforming reaction often suffers from catalyst poisoning due to carbon deposition and the produced synthesis gas has an H2/CO ratio of approximately 1. In the steam reforming reaction, a synthesis gas is produced by supplying steam instead of carbon dioxide in order to prevent the carbon deposition frequently occurring in the carbon dioxide reforming reaction. Although the carbon deposition is suppressed as compared to the carbon dioxide reforming reaction, supply of excess steam is necessary. Further, since the H2/CO ratio of the produced synthesis gas is approximately 3, hydrogen has to be partially removed for use in the Fischer-Tropsch reaction. Although the partial oxidation, autothermal reforming and tri-reforming reactions produce a synthesis gas with an H2/CO ratio of approximately 2, the initial investment is expensive since an oxygen plant for supplying oxygen is necessary. The combined reforming reaction using carbon dioxide and steam can produce a synthesis gas with an H2/CO ratio ranging from 1 to 3 through control of the compositional ratio of reactants. The reaction is also advantageous in that an oxygen plant for supplying oxygen is unnecessary and it is less sensitive to carbon deposition than the carbon dioxide reforming reaction.
In general, nickel-based catalysts are commonly used in the reforming reaction. Although noble metal-based catalysts exhibit better performance in terms of catalytic activity or catalyst poisoning, the nickel-based catalysts are preferred for economic reasons. Accordingly, development of a catalyst for reforming reaction with superior thermal stability and mechanical strength in addition to resistance to carbon deposition is necessary. In this regard, a lot of researches are actively under way to reduce catalyst sintering and carbon deposition.
Korean Patent Publication No. 10-1998-0054391 describes that a Ni/Al2O3 catalyst for carbon dioxide reforming prepared by a coprecipitation method exhibits better activity for the carbon dioxide reforming reaction than a catalyst in which nickel is supported on an alumina support by the impregnation method. Also, it is reported that a catalyst in which nickel is supported on a mesoporous molecular sieve (ZSM-5, MCM-41, KIT-1) by the impregnation method exhibits good activity for the carbon dioxide reforming reaction. As for the combined steam carbon dioxide reforming reaction, it is reported that a Ni/MgO catalyst exhibits better activity and resistance to carbon deposition than a Ni/Al2O3 catalyst [Catalysis Today, 174 (2011), 31]. In particular, a perovskite-type oxide has a redox property and it is possible to prepare oxides containing various elements by introducing other metals into the sites A and B. It is reported that a LaNiO3 perovskite-type catalyst exhibits good activity for the carbon dioxide reforming reaction [Catalysis Today, 107 (2005), 474]. It was also confirmed in the previous study of the inventors of the present invention that LaNiO3 and La1-xSrxNiO3 (x=0-0.5) perovskite-type catalysts exhibit good activity for the combined steam carbon dioxide reforming reaction [Int. Conference on NanoSci. and NanoTech. (2012), in press]. Thus, the present invention is directed to providing a catalyst having good activity for the combined steam carbon dioxide reforming reaction, which is prepared by introducing various materials into perovskite having an ABO3 structure.
Throughout the specification, a number of publications and patent documents are referred to and cited. The disclosure of the cited publications and patent documents is incorporated herein by reference in its entirety to more clearly describe the state of the related art and the present invention.